you can run it indefinitely with the cap loose for diag at up to like 5k feet over sea level. if it still overheats just go straight to the combustion leak tester

This is what i dont get, i just ran this test with the cap off the entire time, the fluid remained blue, but coolant was exploding out of the open cap, while the temperature gauge was still in the middle.

Ive ordered a new cap to knock this off the list, along with a water pump, and some new hoses to stop that leak. I still dont fully understand why the system would overflow and overheat so suddenly versus a consistent rise in temperature.

The temperature gauge is not linear, it reads mid gauge while the temp increases beyond 185F, then jumps to red. You need to monitor the temp via the OBD port.

OP, you might want to invest in an aftermarket gauge that plugs into the OBD-II port and can temporarily, or permanently, sit on the edge of the dash.

i chose permanent. I’m a sucker for gauges. Besides coolant temperature, the one I purchased will display oil temperature, fuel trims, and many other parameters too numerous to list. Most everything except oil pressure.

Amazon sells them for about $40-50.

https://a.co/d/7VFEq6l

I had this too. I was looking for the obvious signs of head gasket issues but not of this issues appeared. Bought a new overflow tank, cap, sender, non helped. After a year searching for the course i went to my specialist and he found the head gasket went wrong. Very small in the cylinder just under the overflow tank. Don't wait too long because it ruins more than a wallet can handle.I was lucky that the head survived but i can mean you have to look for new heads as well. The are the same as the. head b.t.w. and very hard to find.

interesting, what other test could I run to find out if its the headgasket? It passed the combustion gas tester, but that test could have also have been wrong due to the ridiculous way I had to conduct it. If the heads are damaged its whatever as long as the block is fine. I mean id rather not have to replace them but I have alot of wiggle room because I got the car for extremely cheap.

This is classic head gasket failure. Pressurization of the cooling system by exhaust gases. When the engine is cold, yet the expansion tank overflows, something is pressurizing the system. The only thing it could be is exhaust.

If you can't do the exhaust in coolant test, do a compression test on the cylinders. My money is that one or two have issues.

In post #10 Jimmy also pointed out it looks like someone prior to you added “stop leak” to your coolant likely in an attempt to seal the H/gasket leak.

Brian W.

Well the engine wasn't exactly cold, the temperature gauge was in the middle, but the coolant was boiling when it was overflowing out. I'll do the compression test this week and update you.

I'm thinking you might have a blockage in the coolant system (if it's not a head gasket). I would pull the radiator hoses & run a hose (water-not the hose itself ) through the radiator & see if it flows. Maybe someone can post a coolant flow diagram to further diagnose this possibility...

I did not see any mention of the thermostat itself (not the housing) being replaced. If they stick closed, you will get overheating. Usually that should cause the temp gauge to jump to the high position. Do you have an infrared temp gauge? What is the temp of the coolant when it pushes out?

sorry for the delayed response, i dont believe i have a blockage, ive flushed the system 2 times when i replaced the thermostat housing just because i wasn't a fan of how the coolant worked, each time I drained it through the radiator i needed about 2 gallons to refill the system which from my understanding isn't too far from the capacity. Im sure some was trapped in the heater and all that but didn't seem like a full system clog. I'll try running it without the thermostat while I wait for it to warm up for the compression test and see if that ends up saving me the time. I still need to put the new water pump in aswell ive just been so out of time recently. But I'll get this old cat back on the road one way or another

I’m not following , what are you trying to accomplish by leaving out the thermostat ?

Z

just to check if its something as simple as the thermostat, if its stuck by removing it the system would continuously cool and not overheat. If it still over heats than I know it wasn't the problem and then the engine will have PLENTY of heat for the compression test

You want to do the compression test, or any other test with the engine at the proper operational temperature that the engine was designed to run at. Having a functioning thermostat in place is the only way to a proper test.

Leaving the thermostat out altogether will likely keep the engine from getting up to the temp it was designed to run at

Z

So last time I worked on the car was about a week ago, and the coolant system had been thoroughly flushed with distilled water, like ive gone through 5 gallons of water. The system should be solely water at this point. Today i went to pull the thermostat to test it, and also to try the compression test, but it looks like the water answered the question for me. Clearly oil has been seeping into the cooling system all week. Time to buy some headgaskets!

Forgot to update this, a month ago I ended up taking the thermostat out as a hail Mary before I went and ordered the headgaskets. Ended up working perfectly after that, been driving it around for the last month without a single issue. Sorry for wasting everyone's time!

so now you are running without a thermostat ??

Z

so now you are running without a thermostat ??

Z